Understanding Breast Lymph Node Status: What It Means and Why It Matters

Lymph node status is an important part of a breast cancer diagnosis. Learn how doctors assess whether breast cancer has spread to lymph nodes and more

When someone is diagnosed with breast cancer, their oncologist needs to obtain several key pieces of information to determine the stage of the cancer, the most appropriate treatment, and their prognosis. One important piece of information is lymph node status: whether the cancer has spread to nearby lymph nodes, and if so, how many are affected.

These nodes, also called lymph glands, are small bunches of immune cells that help the body fight infection. If and when breast cancer spreads, it usually travels to the lymph nodes under the arm (axillary lymph nodes) first.

Research conducted by BCRF-supported investigators and others has revealed crucial information about the molecular and cellular processes involved in how breast cancer can spread to the lymph nodes. By continuing to advance the understanding of lymphatic spread, researchers may be able to identify new targets for therapy.

Read on to learn what we know so far and how breast cancer with lymph node involvement is diagnosed and treated.

Anatomy of breast lymph nodes

To understand how breast cancer spreads to the lymph nodes, it’s helpful to review the structure and function of lymphatic system. A component of the immune system, the lymphatic system consists of a network of cells, tissue, vessels, and organs that circulate a watery fluid called lymph throughout the body.

Lymph, which originates in the blood as plasma, flows into tiny pores in the capillaries, delivering oxygen and nutrients to your tissues. At the same time, it sweeps away damaged cells including cancer cells, bacteria, viruses, and more. As the lymph travels through lymph vessels, it enters lymph nodes, where it’s “cleaned” by immune cells such as lymphocytes that mark, destroy, and remove the damaged cells and invaders. Once lymph has traveled throughout the body and reaches two ducts in your upper chest (lymphatic duct and thoracic duct), it re-enters the blood and the process repeats.

Lymph nodes are located throughout most the body, but there are specific areas where they’re clustered, including the armpits, neck, and chest. Breast cancer most often spreads to the axillary nodes first, but if the cancer is located closer to the middle of the chest, it may enter the lymph nodes near the breastbone (internal mammary lymph nodes).

What is lymph node status?

Lymph node status, which ranges from N0 to N3, describes whether cancer has spread to the lymph nodes near your breast and the number of nodes affected. It’s part of the  tumor, node, metastasis (TNM) system doctors use to stage breast cancer:

• N0: There is no spread to nearby lymph nodes.
• N1: Cancer has spread to fewer than 3 lymph nodes in the underarm or to any number of internal mammary lymph nodes.
• N2: Cancer has entered 4 to 9 axillary lymph nodes or has enlarged internal mammary lymph nodes.
• N3: The disease has spread to: 1) more than 10 axillary lymph nodes; 2) lymph nodes under the collarbone; 3) at least one axillary lymph node and enlarged internal mammary lymph nodes; 4) at least four axillary lymph nodes and internal mammary lymph nodes as detected by biopsy; or 5) lymph nodes above the collarbone on the same side of the body as the cancer.

Note that if your breast cancer is in the lymph nodes, it does not mean you have metastatic breast cancer (MBC), also referred to as stage 4 breast cancer. MBC is breast cancer that has spread beyond the breast and nearby lymph nodes to other parts of the body, typically the bones, lungs, and liver. Once this occurs, the cancer can be treated but not cured.

How breast cancer spreads to lymph nodes

Breast cancer spreads to the lymph node when cancer cells break away from the main tumor and enter the sentinel lymph node, which is the node located closest to the tumor. The sentinel node is the first of a chain of axillary lymph nodes that filters lymph drainage from the breast and captures cancerous cells. Therefore, it is usually the first node that is affected when breast cancer spreads beyond the breast.

Researchers are currently investigating how lymphatic spread works on a molecular and cellular level. Recent studies have identified lymphatic vascular biomarkers that play a significant role in promoting the formation of new lymphatic vessels from those that already exist (lymphangiogenesis), enabling cancer cells to invade the axillary lymph nodes. Researchers have also discovered certain signaling pathways—sequences of chemical reactions that allow cells to communicate and complete their functions— that encourage lymphatic spread. These pathways may be targets for future breast cancer therapies.

Symptoms and diagnostic methods

There may not be any signs that breast cancer has spread to your lymph nodes. This is typically the case when the spread is just beginning and only a few cancer cells have entered a lymph node.

But as more cells invade, you may notice lumps or swelling in your armpits or around your collarbone that may look like a marble and become very hard. (Normal lymph nodes are merely firm and are shaped like a lima bean). Your doctor will check for these signs during a clinical/manual breast exam. He or she will also order imaging tests, such as a CT or MRI scan or ultrasound, to look for indications that cancer cells are present in your lymph nodes.

To confirm that the cancer cells have spread to your axillary lymph nodes, you’ll need to undergo a lymph node biopsy. Your doctor may do this at the same time he or she biopsies the breast tumor, or when the breast tumor is surgically removed. Types of biopsies include:

Core needle biopsy. A small cylinder of tissue is removed from the node using a hollow needle. Your doctor may use imaging techniques such as ultrasound to help guide the needle to the correct location.

Sentinel lymph node biopsy. During a sentinel lymph node biopsy (SLNB), the surgeon first identifies the sentinel lymph nodes by injecting a substance into the main tumor in the breast. This may be a radioactive substance and/or blue dye, or a liquid that contains coated iron oxide particles. The substance travels in the lymph vessels on the same path the cancer most likely would take if it had spread to the lymph nodes. The surgeon then uses a machine to detect radioactivity or iron oxide particles in the nodes or looks for nodes that have turned blue or brown, if iron oxide particles were injected.

Once the location of the sentinel lymph nodes is identified, the surgeon makes an incision in the area and removes the nodes. These are examined for the presence of cancer cells in a lab by a pathologist. In some cases, this can be done while you’re still on the operating table.

Axillary lymph node dissection. If the SLNB reveals the presence of cancer, your surgeon may then remove anywhere from 10 to 40 more lymph nodes to see if there has been additional spread. This is called axillary lymph node dissection (ALND). If the pathologist cannot examine the nodes during the SLNB, they will be studied in the days following the procedure. If cancer is detected, the surgeon may advise an ALND later to remove more lymph nodes to check for cancer cells.

Treatment options and prognosis

Doctors have a few different treatment options for breast cancer that has spread to the lymph nodes. Surgery—either lumpectomy or mastectomy—is part of most breast cancer patients’ treatment plan, and if there is lymph node involvement, the nodes can be removed via lymph node dissection.

Radiation is often performed following surgery, particularly if the lymph nodes were affected, to destroy any cancer cells that may remain. It can be delivered externally via a machine that delivers radiation beams to the target area, or internally via placement of radioactive seeds or pellets using a catheter.

Chemotherapy may also be recommended if there was lymph node involvement or if your doctor suspects there’s a chance the cancer may have spread beyond the lymph nodes. It’s often advised if the cancer is very aggressive or is negative for estrogen, progesterone, and HER2 receptors.

You may need additional treatments depending on what subtype of breast cancer you have. These may include therapies like monoclonal antibodies and tyrosine kinase inhibitors as well as hormone therapy (tamoxifen, aromatase inhibitors, and more). If you have triple-negative breast cancer (TNBC), you may receive infusions of the immunotherapy drug pembrolizumab.

The five-year relative survival rate for breast cancer with lymph node involvement is 87 percent. However, keep in mind that five-year survival rates are merely estimates based on a large population; they are not personal to you. To provide you with a more accurate prognosis, your doctor will weigh several factors such as your age, overall health, breast cancer subtype, how well the cancer responds to treatment, and more.

BCRF-supported research on lymph node status

Breast cancer that’s diagnosed in its earliest stages is more treatable and curable. BCRF investigators are working to understand how and why breast cancer spreads beyond the breast, including to nearby lymph nodes. They’re researching ways to detect breast cancer as early as possible through better screening and risk assessment and even through simple blood tests.

Ultimately, understanding the underlying processes that cause breast cancer to spread will improve outcomes from the disease and help end metastatic breast cancer.

Donate today and make a difference for people impacted by breast cancer by supporting BCRF and lifesaving research.

Frequently asked questions about lymph node status

1. What does lymph node status mean in breast cancer?
Lymph node status refers to whether breast cancer has spread to nearby lymph nodes. It’s key to determining cancer stage, guiding treatment options, and predicting outcomes. BCRF-supported investigators are working to determine how lymph node involvement happens and devising better strategies for detection.

2. What are lymph node stages in breast cancer?
Lymph node stages describe how far cancer has spread. There may be no lymph node involvement, which is referred to as N0 on your pathology report. N1 to N3 means the cancer has gone to the lymph nodes, with N3 indicating the most extensive spread. These stages are part of the tumor, node, metastasis (TNM) staging system used in diagnosis and treatment planning.

3. What causes swollen lymph nodes in the underarm?
Swollen lymph nodes can result from infection, irritation, allergy, and autoimmune disorders as well as the spread of breast cancer. Not all swelling indicates cancer, but it’s essential to talk to a healthcare provider if swelling persists or is accompanied by other symptoms such as night sweats, persistent fever, and unexplained weight loss.

4. What does a cancerous lymph node feel like?
You may not feel anything if there are only a few cancer cells in your lymph nodes. If there is more extensive spread, lymph nodes that are closer to the surface of your skin, such as those in the armpits, may be swollen. The affected lymph node(s) often hardens and changes in shape from a lima bean to a marble. It usually isn’t painful.